Design principle diagram of forward and reverse circuit of star-delta starting

Figure 1 Figure 1 is a forward and reverse circuit with star-delta starting, that is, the motor starts with star-delta voltage reduction when it rotates forward, and also starts with star-delta voltage reduction when it rotates reversely. As shown in the figure, the main circuit and the control circuit are both forward and reverse circuits in the upper half, and the lower half is the star-delta starting circuit. KM1 and KM2 are the forward and reverse contactors of the motor, KM3 is a star connection contactor, and KM4 is a delta connection contactor. KT is a power-on delay time relay, and its working principle is analyzed below.

Figure 2 Figure 2, close the circuit breaker QS. The red part in the figure is the live part.

Figure 3 Figure 3, first start the motor in forward rotation, press the forward start button SB2, the KM1 coil is energized, KM1-1 is closed, and self-protection. The normally open point of KM1-3 is also closed, starting the star-delta conversion circuit in the lower half, KM3 is energized, and at this time, KM1 and KM3 connect the motor into a forward star connection to start. At the same time, the time relay KT coil is energized and the delay begins, for example, the delay time is set to 10 seconds.

Figure 4 Figure 4, after a delay of 10 seconds, KT-1 is disconnected, KM3 is released, and the normally closed auxiliary contact of KM3 resumes closing. At the same time, KT-2 is closed, so that the coil of KM4 is energized and attracted, and KM4-2 is closed for self-protection. At the same time, KM4-1 is disconnected, so that the coil of the time relay KT is de-energized and reset. At this time, it is converted to KM1 and KM4 to connect the motor to the car for positive rotation angle operation.

Figure 5 Figure 5, the following demonstrates the reverse rotation of the motor. As shown in the figure, press the reverse start button SB3, KM2 is energized and energized, and KM2-2 is closed for self-protection. KM2-3 is also closed, starting the star-angle conversion circuit in the lower part. As with forward rotation, KM3 and KT are first energized, and KM2 and KM3 connect the motor into a reverse star connection for start.

Figure 6 Figure 6, after a delay of 10, KM3 is released and KM4 is energized. At this time, KM2 and KM4 connect the motor to run in reverse angle.